Method and apparatus for synchronizing fast ethernet data packets to radio frames in a wireless metropolitan area network

ABSTRACT

Method and apparatus for synchronizing Fast Ethernet data packets to radio frames in a wireless metropolitan area network. A method of synchronizing Fast Ethernet data packets to radio frames includes receiving Fast Ethernet data packets, storing packet data in a packet buffer according to a first clock signal wherein the first clock signal is derived from the data packets, retrieving the packet data from the packet buffer according to a second clock signal wherein the second clock signal is asynchronous with the first clock signal, and formatting the retrieved packet data according to radio frames. According to another aspect of the invention, a method of synchronizing radio frames to Fast Ethernet data packets includes recovering packet data for Fast Ethernet data packets from radio frames, storing packet data from the radio frames in a packet buffer according to a first clock signal synchronous with the radio frames, retrieving the packet data from the packet buffer according to a second clock signal wherein a frequency of the second clock signal is lower than a frequency of the first clock signal, and forwarding the data packets reconstructed from the radio frames. The method can also include adjusting a frequency of the second clock signal according to an amount of space available in the packet buffer, adjusting an inter-packet gap for the data packets according to an amount of space available in the packet buffer, or pausing the step of forwarding according to an amount of space available in the packet buffer.

This is a Continuation-in-Part of application Ser. No. 08/950,028, filedOct. 14, 1997, the contents of which are hereby incorporated byreference. This application claims the benefit of U.S. ProvisionalApplication Ser. No. 60/086,459, entitled, “Method and Apparatus forWireless Communication of Fast Ethernet Data Packets,” filed May 22,1998.

FIELD OF THE INVENTION

The invention relates to a terminal for a wireless network for ametropolitan area. More particularly, the invention relates to such aterminal including a method and apparatus for synchronizing FastEthernet data packets to radio frames in a wireless metropolitan areanetwork.

BACKGROUND OF THE INVENTION

Computers utilized in modern office environments are typically coupledto a local area network (LAN). The LAN allow users of the computers toshare common resources, such as a common printer included in thenetwork, and allows the users to share information files, such as byincluding one or more file servers in the network. In addition, theusers are typically able to communicate information with each otherthrough electronic messaging. A commonly utilized type of LAN isEthernet. Currently, a variety of products which support Ethernet arecommercially available from a variety of sources. Other types of LANsare also utilized, such as token ring, fiber distributed data interface(FDDI) or asynchronous transfer mode (ATM).

LANs are often connected to a wide area network (WAN) via a telephonemodem. Thus, information is communicated over the WAN via acommunication link provided by a telephone service provider. Thesetelephone links, however, are generally designed to have a bandwidththat is sufficient for voice communication. As such, the rate at whichinformation can be communicated over these telephone links is limited.As computers and computer applications become more sophisticated,however, they tend to generate and process increasingly large amounts ofdata to be communicated. For example, the communication of computergraphics generally requires a large amount of bandwidth relative tovoice communication. Thus, the telephone link can become a datacommunication bottleneck.

Business organizations and their affiliates are often spread overseveral sites in a metropolitan or geographical area. For example, abusiness organization can have a headquarters, one or more branchoffices, and various other facilities. For such business organizations,LANs located at the various sites will generally need to communicateinformation with each other. Wireless communication links for connectinglocal area networks are known. For example, U.S. Pat. No. 4,876,742,entitled “Apparatus and Method for Providing a Wireless Link Between TwoArea Network Systems,” and U.S. Pat. No. 5,436,902, entitled “EthernetExtender,” each disclose a wireless communication link for connectingLANs.

Availability is a measure of the average number of errors which occur indigitally transmitted data. An availability of 99.99 percent is commonlyrequired for radio communications. For an availability of 99.99 percent,the average error rate for digitally communicated data must bemaintained below 1×10⁻⁶ errors per bit, 99.99 percent of the time. Theintegrity of a wireless communication link, however, is largelydependent upon transient environmental conditions, such asprecipitation. Environmental precipitation causes a severe attenuationof the transmitted signal. For example, to maintain an availability of99.99 in the presence of environmental precipitation, the signal must betransmitted at a level that is 24 dB/km higher than otherwise.Therefore, to ensure an acceptable data error rate under all expectedconditions, data is typically communicated over a wireless communicationlink at a relatively high power and at a relatively low rate. The amountof data required to be communicated over the wireless link, however, canvary widely over time and can vary independently of environmentalconditions. In addition, wireless links, especially those operated athigh power levels, can cause interference with other wireless linksoperating in the same geographical area. Thus, the wireless link canbecome a data communication bottleneck.

Therefore, a technique is needed for efficiently and cost effectivelycommunicating data over a wireless link between Ethernet local areanetworks.

A wireless communication system is known having an intermediatefrequency (IF) converter which is connected to a LAN and located insidethe same building as the LAN. The IF converter modulates data signalsfrom the LAN onto a first IF carrier signal. The first IF carrier signalis then routed to a roof-mounted unit via coaxial cabling. Theroof-mounted unit then performs wireless transmission. Similarly, theroof-mounted unit receives wireless transmissions and provides a secondIF carrier signal to the IF converter via the coaxial cabling. The IFconverter demodulates the second IF carrier signal and provides therecovered data signals to the LAN.

This arrangement has a disadvantage in that the required coaxial cablingis relatively expensive in comparison to other types of cables. Inaddition, the IF converter increases the cost of the equipment requiredto be located inside of the building.

Therefore, what is needed is a technique for communicating data over awireless link between local area networks which does not suffer fromthese drawbacks.

Known wireless transmission systems for LAN have a disadvantage in thatthey required conversion from the LAN protocol to an intermediateprotocol prior to wireless transmission. Such known systems performconversion to a telephony protocol or to an asynchronous transfer mode(ATM) protocol.

Therefore, what is needed is a technique for communicating data over awireless link between local area networks which does not suffer fromthese drawbacks.

SUMMARY OF THE INVENTION

A method and apparatus for synchronizing Fast Ethernet data packets toradio frames in a wireless metropolitan area network. According to anaspect of the present invention, a method of synchronizing Fast Ethernetdata packets to radio frames includes steps of receiving Fast Ethernetdata packets, storing packet data from the Fast Ethernet data packets ina packet buffer wherein the step of storing is performed according to afirst clock signal wherein the first clock signal is derived from theFast Ethernet data packets, retrieving the packet data from the packetbuffer thereby forming retrieved packet data wherein the step ofretrieving is performed according to a second clock signal wherein thesecond clock signal is asynchronous with the first clock signal, andformatting the retrieved packet data according to radio frames. The stepof formatting can be performed according to the second clock signal. Thesecond clock signal can be higher than the first clock signal. The stepof formatting can include a step of removing a data valid bit from eachfour-bit portion of retrieved packet data. The step of storing caninclude a step of removing a preamble from each Fast Ethernet datapacket. The step of storing can also include steps of determining alength of the packet data for each Fast Ethernet data packet, andstoring the length of the packet data in a length buffer. The step offormatting can also include a step of inserting the length of the packetinto the radio frame. The step of formatting can also include a step ofinserting a check sum for the length into the radio frame. The check sumcan be a Golay check sum. The step of formatting can include steps ofperforming forward error correction on the retrieved packet data therebyforming error corrected packet data, and inserting the error correctedpacket data into a data field of a radio frame. The step of formattingcan also include a step of randomizing the data field of the radioframe. The radio frames can each have a same length and the step offormatting the retrieved packet data can be performed such thatboundaries for the data packets are not necessarily aligned withboundaries for the radio frames. The step of formatting can also includea step of time-division multiplexing the data packets into the radioframes. The method need not include a step of converting the packet datainto a telephony communication protocol or into an asynchronous transfermode (ATM) protocol prior to communication of the radio frames over thewireless link.

According to another aspect of the present invention, an apparatus forsynchronizing Fast Ethernet data packets to radio frames includes apacket transceiver for detecting Fast Ethernet data packets, a packetbuffer coupled to the packet transceiver for temporarily storing packetdata from the data packets according to a first clock signal derivedfrom the data packets, a packet retriever coupled to the packet bufferfor retrieving the packet data from the packet buffer thereby formingretrieved packet data wherein the packet retriever retrieves the packetdata according to a second clock signal and wherein the second clocksignal is asynchronous with the first clock signal, and a radio framercoupled to the packet retriever for formatting the retrieved packet datainto radio frames. The radio framer can format the retrieved packet datain radio frames according to the second clock signal. The second clocksignal can be higher than the first clock signal. The radio framer canremove a data valid bit from each four-bit portion of the retrievedpacket data. A preamble can be removed from each Fast Ethernet datapacket prior to storage of the packet data in the packet buffer. Theapparatus can also include length buffer coupled to the radio framer forstoring a length of packet data for each Fast Ethernet data packet. Theradio framer can insert the length of packet data for each Fast Ethernetdata packet from the length buffer into the radio frames. The radioframer can inserts into the radio frames a check sum for the length ofpacket data for each Fast Ethernet data packet. The check sum can be aGolay check sum. The radio framer can include a forward error correctorfor correcting errors in the retrieved packet data thereby forming errorcorrected data, and a framing apparatus coupled to the forward errorcorrector for inserting the error corrected data into a data field of aradio frame. The radio framer can also include a randomizer coupled tothe framing apparatus for randomizing the data field of the radio frame.The radio frames can each have a same length and the framing apparatuscan insert the error corrected data into the data field such thatboundaries for the data packets are not necessarily aligned withboundaries for the radio frames. The framing apparatus can time-divisionmultiplex the error corrected data into the radio frames. The packetdata need not be converted into a telephony communication protocol orinto an asynchronous transfer mode (ATM) protocol prior to communicationof the radio frames over the wireless link. The apparatus can alsoinclude a packet counter coupled to the packet buffer for maintaining acount of Fast Ethernet data packets stored in the buffer. The apparatuscan also include arbitration logic means coupled to the packet bufferand to the packet counter for determining when packet data correspondingto a complete Fast Ethernet packet has been stored in the packet bufferand for determining when the packet data corresponding to a completeFast Ethernet packet has been retrieved from the packet buffer. Theapparatus can also include a threshold compare means coupled to thepacket counter for determining when the count is equal to or greaterthan a predetermined threshold number. The apparatus can also include apacket reading means coupled to the threshold compare means forproviding an initiation signal when the count exceeds the predeterminedthreshold. The predetermined threshold can be one. The radio framer canform a frame enable signal when the radio framer is ready to receivepacket data and the apparatus can also include a logic gate coupled toreceive the initiation signal and the frame enable signal, the logicgate for initiating of retrieval of packet data from the packet buffer.

According to a further aspect of the present invention, an apparatus forsynchronizing radio frames to Fast Ethernet data packets includes asynchronizer/de-synchronizer for recovering packet data for FastEthernet data packets from radio frames received from a wireless link, apacket buffer coupled to the synchronizer/desynchronizer for temporarilystoring packet data from the radio frames according to a first clocksignal synchronous with the radio frames, a packet retriever coupled tothe packet buffer for retrieving the packet data from the packet bufferthereby forming retrieved packet data wherein the packet retrieverretrieves the packet data according to a second clock signal and whereina frequency of the second clock signal is lower than a frequency of thefirst clock signal, and an Ethernet transceiver coupled to the packetretriever for forwarding the Fast Ethernet data packets reconstructedfrom the radio frames. The packet retriever can adjust a frequency ofthe second clock signal according to an amount of space available in thepacket buffer. The packet retriever can adjust an inter-packet gap forthe Fast Ethernet data packets according to an amount of space availablein the packet buffer. A layer-two switch at an opposite end of thewireless link can be selectively paused according to an amount of spaceavailable in the packet buffer.

According to yet another aspect of the invention, an apparatus forsynchronizing radio frames to Fast Ethernet data packets includes asynchronizer/de-synchronizer for recovering packet data for FastEthernet data packets from radio frames received from a wireless link, apacket buffer coupled to the synchronizer/desynchronizer for temporarilystoring packet data from the radio frames according to a first clocksignal synchronous with the radio frames, a packet retriever coupled tothe packet buffer for retrieving the packet data from the packet bufferthereby forming retrieved packet data wherein the packet retrieverretrieves the packet data according to a second clock signal and whereinat least sufficient packet data for a complete one of the Fast Ethernetdata packets is stored in the packet buffer prior to the packetretriever retrieving the packet data, and an Ethernet transceivercoupled to the packet retriever for forwarding the Fast Ethernet datapackets reconstructed from the radio frames. The packet retriever canadjust a frequency of the second clock signal according to an amount ofspace available in the packet buffer. The packet retriever can adjust aninter-packet gap for the Ethernet data packets according to an amount ofspace available in the packet buffer. A layer-two switch at an oppositeend of the wireless link can be selectively paused according to anamount of space available in the packet buffer.

According to a still further aspect of the present invention, a methodof synchronizing radio frames to Fast Ethernet data packets includessteps of recovering packet data for Fast Ethernet data packets fromradio frames received from a wireless link, storing packet data from theradio frames in a packet buffer according to a first clock signalsynchronous with the radio frames, retrieving the packet data from thepacket buffer thereby forming retrieved packet data wherein the step ofretrieving is performed according to a second clock signal wherein afrequency of the second clock signal is lower than a frequency of thefirst clock signal, and forwarding the Fast Ethernet data packetsreconstructed from the radio frames. The method can also include a stepof adjusting a frequency of the second clock signal according to anamount of space available in the packet buffer. The method can alsoinclude a step of adjusting an inter-packet gap for the Fast Ethernetdata packets according to an amount of space available in the packetbuffer. The method can also include a step of initiating a pause to alayer-two switch at an opposite end of the wireless link according to anamount of space available in the packet buffer.

According to another aspect of the present invention, a method ofsynchronizing radio frames to Fast Ethernet data packets includes stepsof recovering packet data for Fast Ethernet data packets from radioframes received from a wireless link, clock signal synchronous with theradio frames, retrieving the packet data from the packet buffer therebyforming retrieved packet data wherein the step of retrieving isperformed according to a second clock signal and wherein at leastsufficient packet data for a complete one of the Fast Ethernet datapackets is stored in the packet buffer prior to retrieving the packetdata, and forwarding the Fast Ethernet data packets reconstructed fromthe radio frames. The method can also include a step of adjusting afrequency of the second clock signal according to an amount of spaceavailable in the packet buffer. The method can also include a step ofadjusting an inter-packet gap for the Fast Ethernet data packetsaccording to an amount of space available in the packet buffer. Themethod can also include a step of initiating a pause to a layer-twoswitch at an opposite end of the wireless link according to an amount ofspace available in the packet buffer.

The present invention provides an improvement in that conversion fromthe LAN protocol to an intermediate protocol is not required prior towireless transmission. Rather, the present invention communicates datapackets over a wireless link in a highly efficient manner. Thus,according to the present invention, conversion is not required toconvert the LAN protocol into a telephony communication protocol, suchas PDH (e.g. DS1, DS3, E1 and E3) or SDH (e.g. OC-1, OC-3), or to anasynchronous transfer mode (ATM) protocol prior to communication overthe wireless link.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic block diagram of a pair of wirelessterminals which communicate with each other via a wireless communicationlink in accordance with the present invention.

FIGS. 2A–F illustrate representative metropolitan area network (MAN)topologies according to the present invention.

FIG. 3 illustrates a schematic block diagram of a single wirelessterminal 100 in accordance with the present invention.

FIG. 4 illustrates a schematic block diagram of the digital signalprocessing MAC and radio framer included in the CODEC illustrated inFIG. 2.

FIG. 5 illustrates a frame structure for reformed 100BASE-T Ethernetdata packets according to the present invention.

FIG. 6 illustrates a radio frame according to the present invention.

FIG. 7 illustrates a radio super frame according to the presentinvention.

FIG. 8 illustrates a schematic block diagram of a symbol scrambleraccording to the present invention.

FIG. 9 illustrates a schematic block diagram of a differential encoderand characteristic equations according to the present invention.

FIG. 10 illustrates a schematic block diagram of a differential decoderand characteristic equations according to the present invention.

FIG. 11 illustrates a mapping constellation for a constellation mapperaccording to the present invention.

FIG. 12 illustrates a schematic block diagram of an Ethernet-to-radioframe synchronizing portion of the rate control logic according to thepresent invention.

FIG. 13 illustrates a schematic block diagram of a radioframe-to-Ethernet synchronizing portion of the rate control logicaccording to the present invention.

FIG. 14 illustrates a schematic block diagram of a microwave module andmicrowave antenna according to the present invention.

FIG. 15 illustrates a perspective view of the microwave antenna and ahousing for the outdoor unit according to the present invention.

FIG. 16 illustrates a schematic block diagram of an alternate embodimentof the digital signal processing MAC and radio framer according to thepresent invention.

FIG. 17 illustrates a frame structure for reformed 100BASE-T Ethernetdata packets formed by the MAC and radio framer illustrated in FIG. 14.

FIG. 18 illustrates a schematic block diagram of an adaptivecountermeasures block according to the present invention.

FIG. 19 illustrates a chart of received signal level vs. time as aresult of rain fade.

FIG. 20 illustrates a flow diagram for implementing counter-measuresaccording to the present invention.

FIG. 21 illustrates a point-to-multipoint metropolitan area networkdivided into sectors having inner and outer radii according to thepresent invention.

FIG. 22 illustrates a wireless link between two terminals wherein anunauthorized terminal is attempting to eavesdrop on communicationbetween the two terminals.

FIG. 23 illustrates an embodiment according to the present inventionhaving multiple digital processing MACs multiplexed to a single radioframer.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 illustrates a schematic block diagram of a pair of wirelessterminals 100, 100′ which communicate with each other via abi-directional wireless communication link 102 in accordance with thepresent invention. Though a single wireless communication link 102 isillustrated, it will be apparent that a network of wirelesscommunication links can interconnect a plurality of wireless terminals,thereby forming a wireless metropolitan area network (MAN) in accordancewith the present invention. FIGS. 2A–F illustrate representative MANtopologies which interconnect wireless nodes A–E with wireless linksaccording to the present invention. Each of the nodes A–E can include awireless terminal identical to the terminal 100 or 100′ illustrated inFIG. 1 for terminating each wireless link. It will be apparent thatother MAN topologies can be implemented and that one or more of thenodes A–E can be coupled to one or more other types of networks.

Due to availability of portions of the radio spectrum in the 38 GHzfrequency band, the wireless link 102 illustrated in FIG. 1 preferablyoperates within this frequency band, though another frequency band canbe selected. Different channels within the selected band are assigned tonearby wireless links so as to reduce interference between them. Thechannels are preferably stepped at intervals of 25–50 MHz. Because the38 GHz radio frequency band is susceptible to rain fade, the manner andpath of transmissions via the wireless link 102 are adaptively modifiedfor maintaining a predefined transmission quality in the network inaccordance with the teachings of the parent application Ser. No.08/950,028, filed Oct. 14, 1997, the contents of which are herebyincorporated by reference.

Referring to FIG. 1, the wireless link 102 preferably includes a primaryradio channel 102A which carries full duplex 100 mega-bits-per-second(Mbps) data traffic, including payload data, and an auxiliary radiochannel 102B which carries full-duplex control data for networkmanagement and control over the manner of transmission over the link 102(link control). For example, changes to the manner of transmissioninitiated through link control can include changing transmission power,data bit rate, amplitude modulation scheme, spectrum spreading andtransmission path.

The terminal 100 includes a broadcast device, also referred to herein asan outdoor unit (ODU) 104, which terminates one end of the wireless link102. In the preferred embodiment, the ODU 104 includes a bi-directionalradio antenna and is mounted outdoors on a roof-top mast of a building.Also included in the terminal 100 is an extender device, also referredto herein as a top floor unit (TFU) 106, which is coupled to the ODU viabi- directional communication cables 108, 110 and 112 and by power leads114. The TFU 106 is preferably located indoors of the building havingthe ODU 104 located on its roof and as close as practical to the ODU104. In preferred embodiment, the TFU 106 is located indoors, ideally ina wiring closet, on the top floor of the building. It will be apparentthat the term “top floor unit”, as used herein, refers to the extenderunit 106 and its equivalents regardless of its location relative abuilding. For example, the “top floor unit” is preferably, though notnecessarily, located on the top floor of a building.

The cable 108 carries full-duplex data traffic between the ODU 104 andthe TFU 106 which is received from, or transmitted to, the primary radiochannel 102A. The data traffic communicated via the cable 108 includespayload data for communication over the link 102 and can also includenetwork management and control data. Preferably, data communicated viathe cable 108 is in accordance with a Fast Ethernet standard, 802.3u,adopted by the Institute of Electrical and Electronics Engineers (IEEE),such as 100BASE-TX or 100BASE-T4, which operates at a data rate of 100Mbps. The cable 110 carries half-duplex network management and controldata between the ODU 104 and TFU 106. Preferably, data communicated viathe cable 110 is in accordance with an Ethernet standard, such as10BASE-T, which operates at 10 Mbps. The cable 112 carries serial datafor set-up and maintenance purposes between the ODU 104 and the TFU 106.Preferably, the data communicated via the cable 112 is in accordancewith conventional RS423 serial port communication protocol. The cable114 provides supply power to the ODU 104.

Thus, in the preferred embodiment of the present invention, data iscommunicated between the TFU 106 and the ODU 104 via each of the cables108, 110 and 112 according to baseband communication frequencies. Thisis in contrast to systems which communicate data between an indoor unitand an outdoor unit by modulating such data to intermediate frequencies(IF). The baseband communication aspect of the present invention has anadvantage over such an IF modulation scheme in that implementation ofthe TFU 106 is simplified by the present invention. In addition, thecables 108, 110 and 112 can be of less expensive construction than wouldbe required for IF communication.

A router or switch 116 is coupled to the TFU 106, and hence, to theterminal 100, via cables 118 and 120. The cable 118 preferablycommunicates data in accordance with the 100BASE-TX or T4 Fast Ethernetstandard, while the cable 120 preferably communicates data in accordancewith the 10BASE-T Ethernet standard. Alternately, the cable 118 can be afiber-optic cable, in which case, it preferably communicates data inaccordance with 100BASE-FX Fast Ethernet standard.

A cable 122 is coupled to a serial port of the TFU 106. Preferably, datacommunicated via the cable 122 is in accordance with the RS232 serialport communication protocol. A diagnostic station 124 can be coupled tothe cable 122 for performing diagnostics, set-up, and maintenance of theterminal 100. Because certain aspects of the TFU 106 and ODU 104 canonly be accessed from the diagnostic station 124 security over suchaspects is enhanced by the requirement that the diagnostic station 124be directly connected to the TFU 106 via the cable 122. AC power issupplied to the TFU 106 via a power supply cable 126.

A wired local area network (LAN) 128, such as an Ethernet LAN locatedwithin the building having the terminal 100, can be coupled to therouter or switch 116. In addition, a wide area network (WAN) 130, suchas a telephone service network which provides access to the world wideweb, can be coupled to the LAN 128. Thus, the wireless link 102 can beaccessed from one or more personal computers (PCs), data terminals,workstations or other conventional digital devices included in the LAN128 or WAN 130. A network management system (NMS) 132 is coupled to anyone or more of the router or switch 116, the LAN 128 or the WAN 130. TheNMS 132 accesses the wireless link 102 and the terminals 100, 100′ forperforming network management and link control functions (e.g.collecting data regarding operation of the MAN or changing the manner ofdata transmission over a particular link or links). If the NMS 132 iscoupled to the LAN 128, this access is through the LAN 128. If the NMS132 is coupled to the WAN 130, however, this access is remote via directdial-up through a telephone service provider or via access through theworld wide web. When network management and link control functions areaccessed via the world wide web, a web browser is provided in the NMS132, while a web server 236 (FIG. 3) is provided in the terminal 100. Inthe preferred embodiment, the DS 124 and the NMS 132 are each a personalcomputer, but can be another type of conventional digital device.

The terminal 100′ terminates the opposite end of the link 102, remotefrom the terminal 100. In the preferred embodiment, the link 102 can beup to 4 kilometers or more in dry climates (e.g. Wyoming) whilemaintaining 99.99% link availability and can be up to 1.2 kilometers ormore in wetter climates (e.g. Florida) while maintaining 99.99% linkavailability. Elements illustrated in FIG. 1 having a one-to-onefunctional correspondence are given the same reference numeral, but aredistinguished by the reference numeral being primed or not primed. Note,however, that because any NMS 132, 132′ can access the wirelesscommunication link 102 and both terminals 100, 100′, an NMS 132 or 132′need not be located at each end of the link 102.

FIG. 3 illustrates a schematic block diagram of a single wirelessterminal 100, including a TFU 106 and an ODU 104, in accordance with thepresent invention. The TFU 106 includes a 100BASE-T regenerator 200which is coupled to the cable 118 (FIG. 1) and to the cable 108 (FIG.1). In addition, assuming the cable 118 is a fiber-optic cable the TFU106 includes a converter 202 for converting between fiber-optic cableand Category 5 twisted pair cable. The converter 202 is coupled to thefiber-optic cable 118 and to the regenerator 200. The TFU 106 alsoincludes a 10BASE-T repeater 204 coupled to the cable 120 (FIG. 1) andto the cable 110 (FIG. 1). A converter 206 included in the TFU 106converts between signals in accordance with the RS232 standard andsignals in accordance with the RS423 standard. The converter 206 iscoupled to the cable 122 (FIG. 1) and to the cable 112 (FIG. 1). The TFU106 also includes an alternating-current to direct-current (AC/DC) powerconverter 208 coupled to the cable 126 (FIG. 1) and to the cable 114(FIG. 2). The power converter 208 provides power to the TFU 106 and tothe ODU 104. A status indicator 210 included in the TFU 106 displaysstatus of the TFU 106 via light emitting diodes for diagnostic, set-upand maintenance purposes.

The TFU 106 provides three interfaces to customer equipment, includingthe router or switch 116 (FIG. 1) and the DS 124 (FIG. 1). These includea full-duplex 100 Mbps interface via the regenerator 200, a half-duplex10 Mbps interface via the repeater 204 and an RS232 serial port via theconverter 206. Though the payload data traffic is generally directedthrough the 100 Mbps interface while network management and link controltraffic is generally directed through the 10 Mbps interface, a user ofthe terminal 100 can combine network management and link control signalswith the payload data traffic in the 100 Mbps interface depending uponthe particular capabilities of the router or switch 116 (FIG. 1).

The TFU 106 provides an interface from multiple indoor cables 118, 120,122, 126, to multiple outdoor cables 108, 110, 112 and 114. TFU 106 alsoregenerates/repeats the Ethernet signals in the form of Ethernet datapackets, between the cables 108, 118 and between the cables 110, 120.Thus, the TFU 104 serves to extend the maximum distance possible betweenthe customer equipment, such as the router or switch 116 (FIG. 1), andthe ODU 104. In the preferred embodiment, a distance between thecustomer equipment and the TFU 106 can be up to 100 meters while adistance between the TFU 106 and the ODU 104 can also be up to 100meters. Accordingly, in the preferred embodiment, a distance between thecustomer equipment and the ODU 104 can be up to 200 meters. Because datais communicated between the TFU 106 and ODU 104 at baseband frequencies,however, apparatus for performing IF modulation is not required in theTFU 106.

The ODU 104 includes a 100BASE-T transceiver 212 coupled to the cable108, a 10BASE-T transceiver 214 coupled to the cable 110, an RS423driver 216 coupled to the cable 112 and a DC-to-DC power converter 218coupled to the cable 114. The 100BASE-T transceiver 212, the 10BASE-Ttransceiver 214, and the RS423 driver 216 are each coupled to acoder/decoder (CODEC) 220 included in the ODU 104. The power converter218 provides power to the ODU 104.

The CODEC 220 includes a media access control unit (MAC) 222, having atransmitting portion 224 and a receiving portion 226, a radio framer 228and a micro-processor 230 for controlling operation of the ODU 104. Thetransmitting portion 224 and the receiving portion 226 of the MAC 222are coupled to the 100BASE-T transceiver 212 for communicating Ethernetdata packets with the 100BASE-T transceiver 212. The radio framer 228 iscoupled to the MAC 222 for translating data from the Ethernet datapackets received by the MAC 222 into a radio frames 350 (FIG. 6)suitable for radio frequency modulation and transmission. The radioframer 228 also translates received radio frames 350 (FIG. 6) intopackets which it provides to the MAC 222.

The micro-processor 230 is programmed by software so as to implement aTCP/IP stack 232, a link management (LM) task 234, a HyperText TransferProtocol (HTTP) server 236 and a simple network management protocol(SNMP) agent 238. The micro-processor 230 manages each wireless link ofa network of such wireless links (e.g., a MAN), including a local link102 (FIG. 1) which is coupled directly to the terminal 100. Themicro-processor 230 is accessible via any of the NMS 132 (FIG. 1) andvia the DS 124 (FIG. 1). Thus, the wireless network of links can bemanaged locally, such as via an NMS 132 or DS 124 which is wired to theTFU 106. For this purpose, the microprocessor 230 is assigned anEthernet (medium access control) MAC address. Alternately, the wirelessnetwork of links can be managed remotely, such as via an NMS 132 whichis coupled to the WAN (FIG. 1) and which accesses the micro-processor230 through internet access using TCP/IP (Internet Protocol). The TCP/IPstack 232 provides for this TCP/IP interface through the world wide web.For this purpose, the microprocessor 230 is assigned an internetprotocol (IP) address.

The LM task 234 provides a function of changing the manner in which datais transmitted over a wireless link, initiated by one of the NMS 132,132′. For example, the data rate for the link 102 can be changed via theLM task 132 included in the ODU 104. This can include sending a linkcontrol command over the link 102 to the ODU 104′ (FIG. 1) so that bothterminals 100, 100′ communicate data at the same rate. Such commands arereceived from, and provided to, the microprocessor 230 by a overheadlink management (OH/LM) module 240 included in the radio framer 228.Thus, the radio framer 228 appropriately combines network management andlink control traffic provided by the LM task 234 with payload datareceived from the MAC 222 into radio frames 350 (FIG. 6) forcommunication over the link 102. In addition, the radio framer 228extracts network management and link control traffic from radio frames350 (FIG. 6) received from the link 102 and provides them to the LM task234 of the microprocessor 230 via the OH/LM module 240. While two typesof data traffic (payload and link control) are communicated via radioframes 350 (FIG. 6), the payload data is considered to be communicatedvia the primary channel 102A, while the link control traffic consideredto be communicated via the auxiliary channel 102B. Accordingly, thesetwo channels 102A and 102B are time-division multiplexed.

A graphical user interface by which the micro-processor 230 can beaccessed from an NMS 132, 132′ (FIG. 1) or DS 124, 124′ (FIG. 1) fornetwork management and link control purposes, is preferably achieved bythe HTTP web server software module 236 which is implemented by themicroprocessor 230 located in the ODU 104 and which is assigned a uniqueIP address. The server software 236 operates in conjunction with theTCP/IP stack 232. According to this aspect of the invention, the serversoftware 236 is utilized for providing a graphical user interface forthrough which network management functions are initiated. Thesefunctions include retrieving data representative of network conditionsin the MAN and changing the manner in which data is transmitted across awireless link of the MAN.

Thus, functions for managing the MAN and its wireless links can beaccessed and initiated from network management stations 132, 132′ (NMS)located in various portions of the MAN, utilizing web browser softwareresident in the NMS 132, 132′. This graphical user interface provides auser friendly environment which can operate on, and be accessed by, avariety of different NMS's obtained from a variety of differentmanufacturers. For example, an NMS 132, 132′ can be a workstationmanufactured by Sun Microsystems, a PC manufactured by any one of avariety manufacturers or even a set-top box used in conjunction with atelevision set. Compatibility with the web server is achieved viacommercially available web browser software resident in the NMS 132,132′. This aspect of the present invention addresses compatibilityissues between the NMS 132, 132′, and the terminal 100, 100′.

The SNMP agent 238 located in the ODU 104 maintains a managementinformation database (MIB statistics) which is a collection of managedobjects that correspond to resources of the MAN and of the terminal 100.The SNMP agent 238 can access the MIB to control certain aspects of theMAN and the terminal 100 and can query the MIB for information relatingto the managed objects. The SNMP is accessible through the HTTP server236.

The ODU 104 also includes a transmit modulator (TX mod) 242, a receivedemodulator (RX demod) 244 and a microwave module (MWM) 246. Thetransmit modulator 242 translates from digital baseband output datareceived from the radio framer 228 to analog waveforms suitable forup-conversion to microwave frequencies and eventual transmission overthe wireless link 102. The analog waveforms formed by the transmitmodulator 242 preferably modulate a 490 MHz IF carrier. It will beapparent, however, that a frequency other than 490 MHz can be selectedfor this purpose.

The receive demodulator 244 performs functions which are essentially theopposite of those performed by the transmit modulator 242. In thepreferred embodiment, the receive demodulator 244 receives a 150 MHz IFsignal from the microwave module 246. It will be apparent, however, thata frequency other than 150 MHz can be selected for this purpose. Thereceive demodulator 244 controls the level of the this signal viaautomatic gain control (AGC) and, then, down-converts the signal tobaseband according to coherent carrier recovery techniques and providesthis down-converted signal to the radio framer 228.

The microwave module 246 performs up-conversion to microwave frequencyon the 490 MHz IF output signal generated by the transmit modulator 242and provides this up-converted signal to a microwave antenna 508 (FIG.12) which transmits the data over the link 102. In addition, themicrowave module 246 receives a microwave frequency signal from the link(102, down-converts this signal to a 150 MHz IF signal and, then,provides this down-converted signal to the receive demodulator 244.

FIG. 4 illustrates a schematic block diagram of the digital signalprocessing MAC 222 and radio framer 228 included in the CODEC 220illustrated in FIG. 2. The MAC 222 includes rate control logic 250 andrate buffers 252. The rate control logic 250 receives 100BASE-T Ethernetdata packets at 100 Mbps from the 100BASE-T transceiver 212 (FIG. 3) viaa media independent interface (MII) between the MAC 222 and thetransceiver 212.

Note that 100BASE-T Ethernet data packets are provided to thetransceiver 212 (FIG. 3) as a serial data stream. In accordance with theIEEE 802.3u standard, the serial data stream is encoded utilizing a4B/5B scheme. According to the 4B/5B scheme, each four-bit portion(nibble) of each 100BASE-T data packet is accompanied by a 1-bit datavalid field. Thus, due to the data valid bits, the wire speed for100BASE-T is actually 125 Mbps, though the serial data communicationrate is 100 Mbps assuming the data valid bits are discounted. Thetransceiver 212 converts this serial data stream into parallel four-bitportions of data (nibbles), a data valid signal (RX_DV) and alsorecovers a clock signal from the data stream. The nibbles, data validsignal and clock signal are provided to the MAC 222 by the transceivervia the MII interface.

The data nibbles, data valid signal and recovered clock signal are thensynchronized to a locally generated clock signal. This locally generatedclock signal preferably operates at 27.5 Mhz and is derived from a 55MHz and 10 parts-per-million accuracy crystal oscillator located withinthe CODEC 220 (FIG. 3). The rate control logic 250 detects each100BASE-T Ethernet data packet received from the transceiver 212. In thepreferred embodiment, the rate control block 250 then checks each such100BASE-T Ethernet data packet for errors utilizing the frame checksequence (FCS) appended to each 100BASE-T Ethernet packet and stripseach 100BASE-T Ethernet data packet of its preamble and start-of-framedelimiter (the frame- check sequence FCS for each 100BASE-T Ethernetpacket is preferably retained). The rate control logic 250 also convertseach Ethernet data packet from nibbles to bytes.

The rate control logic 250 calculates the length of each detected100BASE-T Ethernet data packet. The rate control logic 250 alsodetermines whether the packet is too long, too short (a runt packet) oris misaligned.

The rate control logic 250 then temporarily stores the packets in ratebuffers 252. In the preferred embodiment, the bytes for each packet areclocked into the rate buffers 252 according a clock signal recoveredfrom the data. The rate buffers 252 preferably include two first-in,first-out (FIFO) buffers having 16K entries, one for packets beingtransmitted and one for packets being received. The FIFO buffers eachpreferably provides sufficient storage for each entry so that additionalinformation can be stored in the rate buffers 252 along with the byte ofdata. Such additional information preferably includes the data valid bitfor each nibble and an indication of whether the nibble is payload dataor overhead for the 100BASE-T Ethernet packets. For example, theoverhead can include inter-packet gaps codes (e.g. one byte/octet of allzeros with associated data valid bits de-asserted), and start-of-packetcodes. Assuming inter-packet gap codes are stored, preferably only oneinter-packet gap code, representative of the minimum requiredinter-packet gap (e.g. of 0.96 μs), is stored in the rate buffers 252.

The rate control logic 250 then records the previously determined lengthof the 100BASE-T Ethernet data packet in a length and status FIFO buffer254. In addition, the rate control logic 250 stores an indication of thestatus of the packet (e.g. too long, too short or misaligned) in thelength and status buffer 254.

The radio framer 228 is coupled to the MAC 222 and includes the OH/LMblock 240 (FIG. 3), a packet synch/de-synch block 254, a Reed-Solomonencoder/decoder (R-S codec) 258, a framing block 260, a pseudo-randomnumber (PN) randomizer/de-randomizer block 262, a differentialencoder/decoder 264 and a constellation mapper 266.

The packet synch/de-synch block 256 retrieves the stored 100BASE-TEthernet data packets from the rate buffers 252 at an appropriate ratewhich depends, in part, upon the data transmission rate utilized forsending data over the wireless link 102. In the preferred embodiment,removal of data from the rate buffers 252 for an Ethernet packet is notinitiated until the packet has been completely stored. During periodswhen a complete packet is not available from the rate buffers 252, thenan inter-packet gap code is substituted by the packet synch/de-synchblock 254.

In the preferred embodiment of the present invention, the packetsynch/de-synch block 256 reforms the 100BASE-T Ethernet data packetsaccording to a reformed frame structure 300 for 100BASE-T Ethernet datapackets illustrated in FIG. 5. The reformed frame structure 300 includesa synch pattern field 302, a length field 304, a data field 306 and aframe check sequence (FCS) field 308.

Recall that the rate control logic 250 (FIG. 4) strips each 100BASE-TEthernet data packet of its preamble and start-of-frame delimiter priorto storing the packet in the rate buffers 252. Upon retrieving eachpacket from the rate buffers, the packet synch/de-synch block 256 adds asynch pattern in field 302 and a length value in field 304 to thepacket. The length value is retrieved from the length and status buffer254.

In the preferred embodiment, finite state machines control thesynch/de-synch block 256 so as to enable the retrieval of 100BASE-TEthernet packets from the rate buffers 252 along with the length andstatus of each, at a appropriate frequency for forming radio frames 350(FIG. 6). A store and forward technique is applied to 100BASE-T Ethernetpackets which pass through the transmit portion of the rate buffers 252.Thus, data packets to be transmitted across the wireless link 102 arecompletely received into the rate buffers 252 and stored therein priorto being formed into a radio frame 350. A cut-through technique,however, is preferably applied to 100BASE-T data packets which passthrough the receive portion of the rate buffers 252. Thus, data packetsreceived from the wireless link 102 are forwarded to the transceiver 212(FIG. 3) as they received without storing the entire data packet in therate buffers 252.

Table 1 shows the particular bit values for the synch pattern field 302and for the length value field 304 according to the preferred embodimentof the present invention.

TABLE 1 Packet Synch Field 302 Length Field 304 octet octet octet octetoctet octet octet octet 1 2 3 4 5 1 2 3 Bit 1 1 0 1 0 G[11] G[7] G[3] 71 1 0 1 0 G[10] G[6] G[2] 6 0 0 1 0 1 G[9]  G[5] G[1] 5 1 1 0 1 0 G[8] G[4] G[0] 4 0 0 1 0 1 0 L[7] L[3] 3 1 1 0 1 0 L[10] L[6] L[2] 2 1 1 0 10 L[9]  L[5] L[1] 1 0 0 1 0 1 L[8]  L[4] L[0] 0

As shown in Table 1, the synch pattern placed in the synch field 302 ispreferably a five-octet (five-byte) pattern defined by a five-bitWillard code [11010]. Essentially, the Willard code is repeated for eachoctet, but is inverted for two of the five octets. The length valueplaced in the length field 304 is preferably an eleven-bit value L[10:0]which specifies the number of octets (bytes) of payload data containedin the data field 306. Thus, the length value L[10:0] can vary for eachpacket depending upon the length of the data payload included in the100BASE-T Ethernet packet. In the preferred embodiment, a twelve-bitGolay check sum G[11:0] for the length value is stored along with thelength value in the length field 304, as shown in Table 1. Because thelength field 304 is preferably three octets (three bytes) a value ofzero (0) is used a place holder between the length value L[10:0] and theGolay check sum G[11:0].

Referring to FIG. 5, the data payload from the Ethernet packet is storedin the data field 306. Note that 100BASE-T Ethernet data packets areconventionally of variable length. In particular, the data payloadportion for a conventional 100BASE-T Ethernet packet can vary between 64and 1518 octets (bytes). Thus, the length of the data field 304 can varybetween 64 and 1518 bytes.

An important aspect of the reformation of the Ethernet data packets inthe reformed frame structure 300 is the omission of the 1-bit data validfield for each nibble of the Ethernet packet. Rather, the nibbles areplaced contiguously in the data field 306. This omission of the datavalid bits results in a significant savings in bandwidth required fortransmitting the reformed packet frame 300 over the wireless link 102 incomparison to also transmitting the data valid bits over the wirelesslink 102. The FCS sequence is retained for each Ethernet packet andplaced in the FCS field 308.

The packet synch/de-synch block 256 also receives link control data fromthe OH/LM 240 and for combining this link control data with the reformedpacket frames 300 to be communicated over the link 102.

The R-S codec 258 receives the reformed data packet frames 300 and linkcontrol commands from the packet synch/de-synch block 256 and performsReed-Solomon (R-S) forward error correction coding. The R-S encoded datais then provided to the framing block 260 where the R-S encoded data isformatted according to radio frames 350 (FIG. 6).

FIG. 6 illustrates a radio frame 350 according to the present invention.The radio frame 350 includes a synch field 352 for synchronizing areceiver to the radio frame 350, an auxiliary field 354 for networkmanagement and link control traffic which is received from the OH/LM 240to be communicated over the auxiliary channel 102B of the wireless link102, a data field 356, and an R-S parity field 358. The value placed inthe synch field is preferably 47 hex.

In the preferred embodiment, radio frames 350 are continuously formedand transmitted across the wireless link 102 whether or not data from acomplete Ethernet packet is queued in the rate buffers 252 (FIG. 4) tobe placed in reformed packet frames 400. During periods when no reformedpacket frames are available, the data field 356 of the current radioframe 350 is loaded with idle code (all zeros). Similarly, duringperiods when no network management commands are queued to becommunicated via the auxiliary channel 102B, then the auxiliary field354 is loaded with idle code (all zeros).

Recall that reformed packet frames 300 have variable length according tothe preferred embodiment of the present invention. The data field 356 ofeach radio frame 350, however, preferably has a fixed length accordingto the preferred embodiment of the present invention. Accordingly, theR-S encoded data from the R-S codec 258 is placed contiguously in thedata field 356 of each radio frame 350 such that reformed data frame 300boundaries do not have a predefined relationship to radio frame 350boundaries. For example, a reformed data frame 300 can span multipleradio frames 350. Alternately, up to three complete smaller reformeddata frames 300 can be included in a single radio frame 350. Further,during idle periods between communication of reformed packets, an idlecode is preferably transmitted as a place holder within the data field356 of each radio frame 350 to meet the timing requirements needed tosynchronize 100BASE-T Ethernet data packets.

As radio frames 350 are formed, multiples of the radio frames 350 arecombined to form a radio “super frame” 380 (FIG. 7). FIG. 7 illustratesa radio super frame 380 according to the present invention. In thepreferred embodiment, each radio super frame 380 includes 16 consecutiveradio frames 350 (FIG. 6). For the first radio frame 382 of the superframe 380, the value placed in the synch field 352 is inverted (changedto B8 hex). In the second through sixteenth radio frames 384, however,the value placed in the synch field 352 remains unchanged. The valueplaced in the synch field 352 of the first radio frame 386 for a nextradio super frame 388, is also inverted. This inversion of the synchvalue for the first radio frame 350 of each radio super frame 380 allowsthe radio super frames 500 to be detected after reception.

The radio super frame 380 is provided to the PN randomizer/de-randomizer262. The PN randomizer/de-randomizer 262 performs quadrature amplitudemodulation (QAM) scrambling on the entire radio super frame 380 exceptfor the inverted synch values placed in the first synch field 352 ofeach super frame 380. By disabling the PN randomizer/de-randomizer 262for the inverted synch values, the scrambled super frame 380 can bedetected upon reception. In preferred embodiment, the scramblingoperation maps each octet (byte) of the radio super frame 380 (otherthan the inverted synch values) to a two successive four-bit symbolsutilizing a 13th order polynomial, as shown by the schematic blockdiagram of the PN randomizer/de-randomizer 262 according to thepreferred embodiment of the present invention.

Referring to FIG. 8, each octet of the radio super frame 380 (other thanthe inverted synch values) is divided into two successive four-bitportions B[3:0] which are applied to the correspondingly labelled inputsillustrated in FIG. 8. These inputs correspond to in-phase andquadrature (I&Q) symbol components I1, I0, Q1, Q0. A feedback shiftregister 400 generates the specified 13th order polynomial. Contents ofselected memory cells of the feedback shift register 400 areexclusive-OR'd by logical exclusive-OR blocks 402, 404, 406, and 408with each four bit portion b[3:0] of the radio frame. Outputs of theexclusive-OR blocks 402, 404, 406 and 408 form I&Q symbol componentsI1′, I0′, Q1′, Q0′.

The symbol components I1′, I0′, Q1′, Q0′, are applied to thedifferential encoder/decoder block 264 (FIG. 4). FIG. 9 illustrates aschematic block diagram of a differential encoder 264A included in thedifferential encoder/decoder block 264 (FIG. 4) and characteristicequations according to the present invention. The encoder 264A formssignal components I1″, I0″, Q1″, Q0″. In the preferred embodiment, theencoder 264A is implemented by an appropriately preconditioned look-uptable.

The differential encoder encodes the scrambled symbols from the PNrandomizer/de-randomizer 262 such that quantum-phase differencing of thetransmitted symbols according to modulo-π/2 recovers the originalun-encoded data, independent of which of the four possible quantum-phasealignments is selected in the decoder 264B illustrated in FIG. 10.

FIG. 10 illustrates a schematic block diagram of the differentialdecoder 264B included in the differential encoder/decoder 264 (FIG. 4)and characteristic equations according to the present invention. In thepreferred embodiment, the differential decoder 264B is implemented by anappropriately preconditioned look-up table.

The symbol components I1″, I0″, Q1″, Q0″, formed by the encoder 264A areapplied to the constellation mapper 266 (FIG. 4). The constellationmapper 266 maps four-bit portions of the radio frame 350 to sixteendifferent symbols, as shown in FIG. 11, according to quadratureamplitude modulation techniques (16 QAM).

FIG. 11 illustrates a mapping constellation for the constellation mapper266 (FIG. 4) according to the present invention. In the preferredembodiment, this constellation is defined by a standard adopted by theDigital Audio Visual Counsel (DAVIC). The input symbol components I1″,I0″, Q1″, Q0″, are mapped to the output symbol components Is, Im, Qs,Qm, as shown in Table 2. The mapped symbols are then provided by theconstellation mapper 266 (FIG. 4) to the transmit modulator 242 (FIG.3).

TABLE 2 I1″, I0″, Q1″, Q0″ Is, Im, Qs, Qm (input) (output) 0000 10100001 1110 0010 1001 0011 1000 0100 1011 0101 1111 0110 1101 0111 11001000 0110 1001 0111 1010 0101 1011 0001 1100 0010 1101 0011 1110 01001111 0000

Received radio super frames 380 (FIG. 7) are provided to theconstellation mapper 266 (FIG. 4) from the receive de-modulator 244(FIG. 3). During radio super frame 380 reception, each radio super frame380 is converted back from the symbols Is, Im, Qs, Qm, into the symbolcomponents I1″, I0″, Q1″, Q0″, by the constellation mapper 262performing a reverse of the mapping operation according to therelationships shown in Table 2.

In the preferred embodiment of the present invention, the QAM format canbe altered dynamically under control of the microprocessor 230 basedupon rain fade or interference detected through bit error rates (BER) orupon receiving a link control command. For example the QAM format can bedynamically altered from 16 QAM to 4 QAM. Alternately, the QAM formatcan be changed from 16 QAM to 4 QAM and with the application of spectrumspreading. As a result, the data transmission bit rate falls, however,the error rate would be expected to fall also. Conversely, the QAMformat can be dynamically altered from 16 QAM to 64 QAM which results ina higher data transmission bit rate.

Then, the differential decoder 264B (FIG. 10) decodes the symbolcomponents I1″, I0″, Q1″, Q0″, into the symbol components I1′, I0′, Q1′,Q0′. Next, the radio super frame 380 is detected by the inverted synchvalues for the first radio frame of each super frame 380. The symbolcomponents I1′, I0′, Q1′, Q0′, are then provided to the PNrandomizer/de- randomizer 262 (FIG. 4) which converts them to the backinto the original two successive four-bit portions b[3:0] for each octetof each radio frame 350 (FIG. 6) of the radio super frame 380 (FIG. 7).

The radio frame 350 is then synchronized to the radio super frame 380 bydetecting the non-inverted synch value in the field 352 (FIG. 6) foreach radio frame 350. Forward error correction is performed by the R-Scodec 258 (FIG. 4). For each radio frame 350 having an error which isuncorrectable by the R-S codec 258, the R-S codec 258 provides anindication, preferably by setting a flag, which is stored in the ratebuffers 252 along with the affected packet data. For each Ethernetpacket formed by the rate control logic 250 which is affected by such anuncorrected error as flagged by the R-S codec 258 (FIG. 4), the transmiterror signal TX ER provided to the transceiver 212 (FIG. 3) via the MIIinterface, is asserted. A link-layer response can then be applied tocause the packet to be resent.

The reformed data frames 300 are then passed from the R-S codec to thepacket synch/de-synch block 256. In the packet synch/de-synch block 256,the reformed data frames 300 (FIG. 5), as well as network management andcontrol data, are detected and extracted from the radio frame 350structure. For the reformed data frames 300, this is accomplished by awindowed search technique which utilizes matched filter correlation. Thesearch technique is utilized to locate the five-octet synch value in thesynch field 302 (based on the Willard code) for each reformed data frame300. When packet synchronization is maintained, the search windowpreferably encompasses only inter-packet gap periods (when the datafield 356 of the radio frame 350 contains the idle code). During periodswhen packet synchronization is not detected, however, the search windowis expanded to encompass the entire packet. Once synchronization isobtained, the window is again reduced.

Correlation searching is performed by the packet synch/de-synch block256 utilizing a matched filter which performs correlation on anoctet-by-octet basis. Accumulation by addition is performed on 40 bitsof data at a time (5 bytes), as octets slide through the matched filter.The accumulated value is compared to a predetermined threshold for eachoctet. When the threshold is exceeded, the start of a reformed dataframe 300 is indicated.

Once a synch value is detected, the length value for the packet andGolay code are read from the length field 304. The length value isverified utilizing the Golay code. If necessary, the length value iscorrected utilizing the Golay code. If the length value is corrupted anduncorrectable, however, the packet is disregarded while searching for anext synch value continues.

Assuming the length value is correct or correctable, the reformed dataframe 300 is loaded to the rate buffers 252 by the packet synch/de-synchblock 256 in eight-bit portions (bytes) for processing into a 100BASE-TEthernet packet. From the length value, the data valid bit for each byteis also re-generated and stored in the rate buffers 252. A singleinter-packet gap code is stored in the rate buffers 252 to separate eachpacket. Network management and link control data from the auxiliaryfield 354 of each received radio frame 350 is provided to themicroprocessor 230 (FIG. 3) through time-division de-multiplexing.

Then, searching for a next synch value is disabled until the end of thereformed data frame 300, as indicated by the correct or corrected lengthvalue.

Reformed data frames 300 are retrieved from the packet buffer 252 undercontrol of the rate control logic 250 and returned to conventional100BASE-T Ethernet format for the MII interface with the transceiver 212(FIG. 3). This is accomplished by restoring the preamble andstart-of-frame delimiter for each 100BASE-T Ethernet packet. Then, theconventional 100BASE-T Ethernet packets are provided to the 10BASE-Ttransceiver 212 (FIG. 3) at a rate appropriate to the 100BASE-Ttransceiver 212. The 100BASE-T transceiver 212 then communicates thepackets to the TFU (FIGS. 1 and 3). In the preferred embodiment, therate control logic 250 includes a finite state machine for performingthe function of retrieving the Ethernet packets from the rate buffers252 and providing them to the 100BASE-T transceiver 212. Thus, the ratecontrol logic 250 synchronizes the packets to a clock signal utilizedfor communication of the 100BASE-T data packets with the locallygenerated clock signal which is utilized for forming and communicatingradio frames 350 (FIG. 6).

Referring to FIGS. 3 and 4, in the preferred embodiment, the transmitmodulator 242 receives four-bit symbols from the constellation mapper266 of the radio framer 228 in the CODEC 220 at 27.5 Mbaud. Each symbolis converted to a complex in-phase and quadrature (I&Q) voltage and,then, pulse-shaped utilizing a square-root cosine filter in the transmitmodulator 242. Finally, the symbol modulates a 490 MHz intermediatefrequency (IF) output signal. The output level of the signal formed bythe transmit modulator 242 is selectively adjustable over a continuousrange under control of the micro-processor 230. Adjustments in theoutput level are preferably made in response to detected rain fade,detected interference or in response to a link control command. Themodulated IF signal formed by the transmit modulator 242 is supplied tothe microwave module 246.

The receive demodulator 244 preferably includes a 0-dB/20-dB IFattenuator in the receive path which is selectable under control of themicro-processor 230 depending upon the range of the link 102. Typically,this attenuator is set for 0-dB. For link ranges of less thanapproximately 50 meters, however, the attenuator is preferably set for20-dB attenuation. The receive demodulator 244 performs adaptive slopeequalization to minimize effects of distortion caused by transmissionover the link 102. Further, the receive demodulator 244 preferably alsoincludes an adaptive time-domain equalizer to perform symbolsynchronization, and a matched-filter square-root-raised-cosine processis applied to minimize inter-symbol interference.

FIG. 12 illustrates a schematic block diagram of an Ethernet-to-radioframe synchronizing portion 268 of the rate control logic 250 (FIG. 4)and transmit buffer 252A according to the present invention. Thetransmit buffer 252A forms a portion of the rate buffers 252 (FIG. 4).100BASE-T Fast Ethernet packets and a receive data valid signal RXDV arereceived into the transmit buffer 252A from the transceiver 212, asexplained above in reference to FIG. 4. In addition, a clock signal at25 MHz is derived from the incoming data packet and utilized forclocking the incoming Ethernet data packets into the transmit buffer252A.

The receive data valid signal RXDV is provided to a first input of anarbitration logic block 270. In response to a complete Ethernet packetbeing stored in the transmit buffer 252A, as indicated by the data validsignal RXDV, the arbitration logic 270 instructs a packet counter 272 toincrement a count by one. As Ethernet packets are retrieved from thetransmit buffer 252A, a delayed data valid signal is also retrieved fromthe transmit buffer 252A. This delayed data valid signal is applied to asecond input to the arbitration logic block 270. In response to acomplete Ethernet data packet being removed from the transmit buffers252A as it is supplied to the synch/de-synch logic block 256, asindicated by the delayed data valid signal, the arbitration logic block282 instructs the packet counter 272 to decrement the count by one.Thus, the packet counter 272 maintains a current count of completeEthernet data packets in the transmit buffer 252A.

This count is provided by the packet counter 272 to a threshold compareblock 274. The threshold compare block 274 notifies a read packet statemachine 276 when a sufficient number of complete Ethernet packets arestored in the transmit buffer 252A to initiate retrieval of the packetsfrom the transmit buffer 252A. In the preferred embodiment, only onecomplete Ethernet packet need be stored in the transmit buffer 252A toinitiate the read packet state machine 276 to retrieve the packet. Onceinitiated to retrieve a packet, the read state machine 276 activates afirst input to a logic AND gate 278. A second input to the logic ANDgate 278 receives a read frame enable signal from the synch/de-synchlogic 256 (FIG. 4). This read frame enable signal is activated when thesynch/de-synch logic 256 is ready to receive the Ethernet packet datafor insertion into a radio frame 350 (FIG. 6).

An output of the logic AND gate 278 is coupled to a read input of thetransmit buffer 252A for retrieving the packet from the transmit buffer252A. As it is being retrieved, the packet is provided to thesynch/de-synch logic 256.

An important aspect of the Ethernet-to-radio frame synchronizing portion268 of the rate control logic 250 (FIG. 4) is that it synchronizes thereceiving of Ethernet data packets according to 25 MHz clock signalwhich is asynchronous with the locally generated clock signal. Note thatthe 25 MHz clock signal is derived from the incoming Ethernet datapackets and is applied to the transmit buffer 252A for storing thepacket data while the locally generated clock signal is applied to thetransmit buffer 252A for retrieving Ethernet packet data from thetransmit buffer. Thus, the arbitration logic, packet counter 272 andthreshold compare logic 274 operate according to the derived 25 MHzclock, while the read packet state machine 276 and the radio framer 228(FIG. 4) operate according to the locally generated clock.

In the preferred embodiment, the locally generated clock signal is 27.5MHz. Because the locally generated clock signal is at a higher rate thanthe clock signal derived from the incoming Ethernet packets, in absenceof the synchronizing portion 268 of the rate control logic 250, it wouldbe possible for the transmit buffer 252A to become empty while anEthernet packet is still being received into the transmit buffer 252A.Thus, the synchronizing portion 268 of the rate control logic 250 avoidsthis potential problem.

Assuming that an adaptive counter measure is employed which reduces therate at which radio frames 350 (FIG. 6) are formed, this also reducesthe rate at which the data from Ethernet packets is retrieved from thetransmit buffer 252A. Assuming this rate is below 25 MHz (e.g. 13.75MHz), then a complete packet need not be stored in the transmit buffer252A prior to initiating retrieval of such a packet. In the preferredembodiments under such circumstances, cut-through is employed whereinthe incoming Ethernet data packet is supplied to the radio framer 228(FIG. 4) prior to the complete packet being received into the transmitbuffer 252A.

FIG. 13 illustrates a schematic block diagram of a radioframe-to-Ethernet synchronizing portion 280 of the rate control logic250 (FIG. 4) according to the present invention. The receive buffer 252Bforms a portion of the rate buffers 252 (FIG. 4). 100BASE-T FastEthernet packets recovered from radio frames 350 (FIG. 6), and arecovered receive data valid signal RXDV, are received into the receivebuffer 252B from the synch/de-synch block 256, as explained above inreference to FIG. 4. The internally generated clock signal at 27.5 MHzis synchronous with the radio frames 350 (FIG. 6) and utilized forclocking the incoming Ethernet data packets into the receive buffer252B. Ethernet data packets stored in the receive buffer 252B areretrieved and provided to the transceiver 212 (FIG. 3) according to a 25MHz clock.

If no spectrum spreading is employed for data communicated via the link102, then the clock signal utilized for clocking data into the receivebuffer 252B preferably operates at 27.5 MHz. Because the clock signalutilized for retrieving data from the receive buffer 252B preferablyoperates at 25 MHz, there is no possibility that the receive buffer 252Bwill become empty while an Ethernet packet is still being received intothe receive buffer 252B.

However, in the event that spectrum spreading is employed for datacommunicated via the link 102, however, the clock signal applied to thereceive buffer 252B can operate at a lower frequency (e.g. 13.75 MHz),that is synchronous with the internally generated 27.5 MHz clock signal.In which case, it would be possible for the receive buffer 252B tobecome empty while an Ethernet packet is still being received into thereceive buffer 252B. Thus, the synchronizing portion 280 of the ratecontrol logic 250 avoids this potential problem, as explained below.

The recovered receive data valid signal is provided by thesynch/de-synch block 256 (FIG. 4) to a first input of an arbitrationlogic block 282 and to a read packet state machine 288. In response to acomplete Ethernet packet being stored in the receive buffer 252B, asindicated by the recovered data valid signal, the arbitration logic 282instructs a packet counter 284 to increment a count by one. As Ethernetpackets are retrieved from the receive buffer 252B, a data valid signalRXDV is also retrieved from the receive buffer 252B. This data validsignal RXDV is utilized by the transceiver 212 (FIG. 3) and applied to asecond input to the arbitration logic block 282. In response to acomplete Ethernet data packet being removed from the receive buffer252B, and supplied to the transceiver 212 (FIG. 3), as indicated by thedata valid signal RXDV, the arbitration logic block 282 instructs thepacket counter 284 to decrement the count by one. Thus, the packetcounter 284 maintains a current count of complete Ethernet data packetsin the receive buffer 252B.

This count is provided by the packet counter 284 to a threshold compareblock 286. The threshold compare block 286 notifies a read packet statemachine 288 when a sufficient number of complete Ethernet packets arestored in the receive buffer 252B to initiate retrieval of the packetsfrom the receive buffer 252B. In the preferred embodiment, only onecomplete Ethernet packet need be stored in the receive buffer 252B toinitiate the read packet state machine 288 to retrieve the packet. Onceinitiated to retrieve a packet, the read state machine 288 activates afirst input to a logic AND gate 290. A second input to the logic ANDgate 290 receives a LAN read clock enable signal from the transceiver212 (FIG. 3). This LAN read clock enable signal is activated when thetransceiver 212 is ready to receive the Ethernet packet data forcommunication to the TFU 106 (FIG. 1).

An output of the logic AND gate 290 is coupled to a read input of thereceive buffer 252B for retrieving the packet from the receive buffer252B. As it is being retrieved, the packet is provided to thetransceiver 212. Accordingly, this aspect of the present inventionprevents the receive buffer 252B from being emptied while a packet isbeing provided from the receive buffer 252B to the transceiver 212 (FIG.3).

A first alternate approach for avoiding overflow in the receive buffer252B of the terminal 100 during periods when data is being communicatedover the wireless link 102 according to maximum transmission rates canbe implemented when an Ethernet data source (e.g. a terminal in the LAN128′) is operating at a slightly higher rate than the reference clockutilized for removing data from the receive buffer 252B. This approachincludes monitoring the current depth of the receive buffer 252B, and asthe amount of occupied storage space increases, then the transmissionrate of the Ethernet data source is adjusted upward utilizing a voltagecontrolled oscillator. As the amount of occupied storage spacedecreases, then the transmission rate of the transceiver 212 is adjusteddownward. When the buffer is nearly empty, the transmission rate is setto the nominal level of 25 Mhz. Both the originating and local frequencyreferences must be within 100 parts per million high or low of the IEEE802.3 Ethernet specified 25 MHz.

A second alternate approach for avoiding overflow in the receive buffer252B of the terminal 100 during periods when data is being communicatedover the wireless link 102 according to maximum transmission rates,involves reducing the minimum inter-packet gap utilized for forwardingpackets removed from the receive buffer 252B. For example, rather thanutilizing 12 byte-times to represent the inter-packet gap, theinter-packet can be represented by 11 byte-times. This may result in aviolation of the IEEE 802.3 standard for the minimum inter-packet gap,however, this result is expected to be more desirable than the loss ofpacket data should the receive buffer 252B overflow.

A third alternate approach for avoiding overflow in the receive buffer252B of the terminal 100 during periods when data is being communicatedover the wireless link 102 according to maximum transmission rates, isfor the microprocessor 230 of the terminal 100 to send a link controlcommand to the terminal 100′. This link control command provides a pausepacket to the layer-two switch 600′ (the layer-two switch 600′ andassociated packet buffers 602′ are not shown, however, because theterminal 100′ is identical to the terminal 100, it will be understoodthat the layer-two switch 600 and packet buffers 602 illustrated in FIG.16 have identical counter-parts in the terminal 100′, referred to hereinas 600′ and 602′). The pause packet causes the switch 600′ totemporarily store packets in its associated packet buffers 602′ ratherthan sending such packets to the receive buffer 252B.

FIG. 14 illustrates a schematic block diagram of the microwave module(MWM) 246 (FIG. 3) and microwave antenna 508 according to the presentinvention. The MWM module 246 constitutes a wireless transceiver forimplementing wireless communication over the link 102 (FIG. 1). The MWM246 includes a transmit up-converter (TX-U/C) 500 coupled to receivesignals from the transmit modulator 242. The TX U/C 500 up-converts 490MHz IF signals received from the transmit modulator 242 to microwavefrequency for transmission over the link 102. In the preferredembodiment, the frequency of transmission over the link 102 isselectable under control of the micro-processor 230 in 12.5 MHz stepsacross two adjacent microwave bands (e.g. 38.6–39.2 GHz and 39.3–40.0GHz).

A transmit power amplifier (TX-P/A) 502 coupled to the transmitup-converter 500 amplifies the microwave signals provided by thetransmit up-converter 500 to an appropriate level. In the preferredembodiment, the transmit power amplifier 502 has a 1-dB compressionpoint at about 17 dBm. The nominal power is preferably set to 11 dBm,however, the transmit power is selectively controllable by themicro-processor 230 in response to detected rain fade, detectedinterference or in response to a link control command.

A transmit sub-band filter 504 coupled to the output of the transmitpower amplifier 502 filters unwanted frequencies from the microwavesignal to be transmitted over the link 102. The microwave module 246includes a di-plexer 506 coupled to the transmit sub-band filter 504.The di-plexer 506 couples the microwave module 246 to the microwaveantenna 508 for full-duplex communication over the link 102 by themicrowave module 246. The antenna 508 transmits microwave signals overthe link 102 and receives microwave signals from the link 102.

A microwave signal received from the link 102 by the antenna 508 isprovided to a receive sub-band filter 510 via the di-plexer 506. Thereceive sub-band filter 510 filters unwanted frequencies from thereceived signal and provides a filtered signal to a low noise amplifier(LNA) 512. Then, the received signal is down-converted, preferably to150 MHz IF by a receive down-converter (RX D/C) 514. It will beapparent, however, that a frequency other than 150 MHz can be selected.An intermediate frequency automatic gain control (IF AGC) circuit 516adjusts the level of the down-converted signal to a predetermined level.An output formed by the IF AGC 516 circuit 514 is provided to thereceive demodulator 244.

According to the preferred embodiment of the present invention, amicrowave frequency synthesizer 518 included in the microwave module 246is locked to a precision crystal reference signal and is digitallycontrolled by the microprocessor 230 (FIG. 3) with a 12.5 Mhz stepcapability. Two outputs of the frequency synthesizer 516 are each lockedto the same crystal reference signal and provided to the transmitup-converter 500 and to the receive down-converter 514 for performingup-conversion and down-conversion, respectively.

FIG. 15 illustrates a perspective view of the microwave antenna 508 anda housing 550 for the outdoor unit 104 (FIGS. 1 and 3) according to thepresent invention. The housing 550 protects the ODU 104 fromenvironmental conditions, such a rain, snow and sunlight, which can beencountered on roof-tops where the ODU 104 is typically positioned. Thehousing 550 includes a flange 552 for attaching the antenna 508 andcooling fins 554 for dissipating heat generated by the electricalcircuits of the ODU 104. A cable 556 which is preferablyweather-resistant and electrically-shielded, extends between, andelectrically connects, the ODU 104 to the TFU 106 (FIGS. 1 and 3). Thus,the cable 556 includes each of the cables 108, 110, 112 and 114 (FIGS. 1and 3).

FIG. 16 illustrates a schematic block diagram of an alternate embodimentof the digital signal processing MAC 222′ and radio framer 228′according to the present invention. Elements illustrated in FIG. 16having a one-to-one functional correspondence with elements illustratedin FIG. 4 are given the same reference numeral, but are distinguished bythe reference numeral being primed. In one respect, the arrangementillustrated in FIG. 16 differs from that illustrated in FIG. 4 in that alayer-two switch 600 and associated packet buffer 602 are added.

According to the embodiment of the MAC 222′ illustrated in FIG. 16, theEthernet switch 600 is coupled to the transceivers 212, 214 (FIG. 3) andto packet buffers 602. The packet buffers 602 provide a temporarystorage for packets while being directed through the switch 600. Theswitch 600 is also coupled to the microprocessor 230 via an interface604 and to the rate control logic 250′ via an interface 606. The switch600 can be a conventional layer-two Ethernet network switch having a100BASE-T port coupled to the cable 108 and a 10BASE-T port coupled tothe cable 110. In the preferred embodiment, the switch 600 also includesa 10BASE-T port which is coupled to the microprocessor 230 via theinterface 604 and a 100BASE-T MII port which is coupled to the ratecontrol logic 250′ via the interface 606.

Network management and link control traffic in the form of Ethernetpackets received by the switch 600 from the transceiver 212, thetransceiver 214, or the interface 606, and which include the MAC addressof the microprocessor 230 as a destination address are directed to themicroprocessor 230 via the interface 604 by the switch 600. Similarly,the microprocessor 230 sends Ethernet packets to the rate control logic250′ via the switch 600 for communication over the link 102 and to thetransceivers 212, 214 via the switch 600 for communication with therouter or switch 116 (FIG. 1).

In the preferred embodiment, the switch 600 implements a flow controltechnique in accordance with IEEE 802.3x. According to the presentinvention, the flow control technique is selectively initiated by therate control logic 250′ sending a pause packet to the switch 600 via theinterface 606. Each pause packet includes an indication of a how longthe flow control technique is to remain active. In response to receivingthe pause packet, the switch 600 does not provide packets which arereceived from the transceivers 212, 214 or from the interface 604 to theinterface 606. Rather, when the flow control technique is active, theswitch 600 temporarily queues such packets by storing them in the packetbuffers 602. The pause signal can preferably be initiated for severalhundred milli-seconds while packets are received from the transceivers212, 214 or from the interface 604 without loss of any such packets.When the indicated time expires, the flow control technique isdeactivated. Upon deactivation of the flow control technique, the switch600 retrieves the queued packets from the packet buffers 602 andprovides them to the rate control logic 250′ via the interface 606.

The rate control logic 250′ sends a pause packet with an indicatedactivation period in response to a halt control signal received from therate buffers 252′ via a signal line 608. When activated, the halt signalprovided via the signal line 608 indicates that the rate buffers 252′are nearly full. The indicated activation period included in the pausepacket is appropriate to allow sufficient data to be removed from therate buffers 252′ and communicated over the link 102 via radio frames350.

As an example of operation of the MAC 222′, assume that rain fade orinterference is detected in the link 102 by an increase in a measuredbit error rate (BER). In response, a link control command is issued bythe microprocessor 230 which causes the data rate for the link 102 to bereduced. As a result of this lower data rate for the link 102, radioframes 350 are formed less quickly and, thus, data is removed from therate buffers 252′ at a lower rate. If the reduced data rate results inthe rate buffers 252′ becoming nearly full, the rate buffers 252′activate the halt signal via the signal line 608. In response, the ratecontrol logic 250′ sends a pause packet to the switch 600. Then, whileflow control is active, packets received from the transceiver 212, 214or the interface 604 for communication over the link 102 are temporarilyqueued in the packet buffers 602. Accordingly, the MAC 222′ according tothe present invention implements a flow control technique for adapting acurrent rate of data transmission over the link 102 to a rate at whichEthernet packets are received by the MAC 222′ from the TFU 106 (FIGS. 1and 3), without loss of the Ethernet packets.

In addition, the embodiment of the MAC 222′ illustrated in FIG. 16includes an encryption/decryption block 612 coupled between the ratecontrol logic 250′ and the rate buffers 252′. Accordingly, for packetsto be transmitted over the link 102, the encryption/decryption block 612encrypts the Ethernet data packets prior to temporarily storing the datapacket in the rate buffers 252′. Conversely, Ethernet packets receivedfrom the link 102 are decrypted by the encryption/decryption block 612before being provided to the switch 600. A memory buffer 614 coupled tothe encryption/decryption block 612 provides a temporary memory storefor use during encryption/decryption of the Ethernet packets. Anencryption start control signal line 610 coupled between theencryption/decryption block 612 and the length/status buffer 254′ isutilized by the encryption/decryption block 612 to instruct thelength/status buffer 254′ to provide an encryption tag and sequencenumber to the packet synch/de-synch block 256′. This arrangement whichincludes the encryption/decryption block 612 provides an advantage overthe arrangement illustrated in FIG. 4 in that data security is enhanced.

FIG. 17 illustrates a frame structure 700 for reformed 100BASE-TEthernet data packets formed by the MAC 222′ and radio framer 228′illustrated in FIG. 16. When the packet is removed from the rate buffers252′ and reformed for insertion to a radio frame 350 (FIG. 6), theencryption tag and sequence number provided by the length/status buffer254′ (FIG. 16) are appended to the reformed packet frame 700 in anencryption tag field 702 and a sequence number field 704, respectively.The encryption tag indicates an appropriate key box utilized to encryptthe data while the sequence number provides synchronization informationto the terminal which receives the reformed Ethernet data frame 700 fromthe wireless link 102. Fields of the reformed packet frame 700illustrated in FIG. 17 which have one-to-one functional correspondencewith those illustrated in FIG. 5 are given the same reference numeralprimed.

Referring to FIG. 16, this arrangement also differs from thatillustrated in FIG. 4 in that the PN randomizer/de-randomizer 262 andthe differential encoder/decoder 264 are omitted and, instead, anadaptive countermeasures block 616 takes their place. The adaptivecountermeasures block 616 responds to a rate change command issued bythe microprocessor 230 by changing the rate at which data iscommunicated over the wireless link 102. The rate at which data iscommunicated can be in response to a detected increase in BER due torain fade or can be to reduce interference with nearby wireless links,such as to reduce interference between subscriber terminals in apoint-to-multipoint network.

FIG. 18 illustrates a schematic block diagram of the adaptivecountermeasures block 616 according to the present invention. Amultiplexer 750 is coupled to the framing block 260′ (FIG. 16) forcommunicating radio super frames 380 (FIG. 7) with the framing block260′. A first PN randomizer/de-randomizer 262A′, a second PNrandomizer/de-randomizer 262B′ and a first differential encoder/de-coder264A′ are each coupled to receive selected radio super frames 380 fromthe multiplexer 750 depending upon conditioning of the multiplexer 750by the rate change control signal.

In the preferred embodiment, the PN randomizer/de-randomizers 262A′,262B, 262C′ perform scrambling on the radio super frames 380 in anidentical manner to the PN randomizer/de-randomizer 262 illustrated inFIGS. 4 and 8. Super frames 380 scrambled by the PNrandomizer/de-randomizer 262A′ are provided to a second differentialencoder/decoder 264B′. The differential encoder/decoders 264A′, 264B′and 264C′ preferably perform encoding and decoding in an identicalmanner to the differential encoder/de-coder 264 illustrated in FIG. 4.Then, super frames 380 encoded by the second encoder/decoder 264B′ areprovided to a QAM constellation mapper 266′. The QAM constellationmapper 266′ preferably performs QAM constellation mapping in anidentical manner to the QAM constellation mapper 266 illustrated inFIGS. 4 and 16. A multiplexer 756 is coupled to the QAM constellationmapper 266′ for communicating encoded radio super frames 380 with the Rxdemodulator 244 (FIG. 3) and Tx modulator 242 (FIG. 3). Thus, when afirst path through the PN randomizer/de-randomizer 262A′, the seconddifferential encoder/decoder 264B′ and QAM constellation mapper 266′ isselected, radio super frames 380 are conditioned identically fortransmission and reception as when passing through the PNrandomizer/de-randomizer 262, differential encoder/decoder 264 and QAMconstellation mapper illustrated in FIG. 4. In the preferred embodiment,the first path conditions the radio super frames 380 according to 16QAM.

The third differential encoder/decoder 264C′ is coupled to the PNrandomizer/de-randomizer 262B′ and to a quadrature phase-shift (QPSK)constellation mapper 752A. The QPSK constellation mapper 752A mapsportions of the radio frame 350 to QPSK symbols according to quadraturephase-shift keying techniques (QPSK). Super frames 380 are communicatedbetween the QPSK constellation mapper 752A and the multiplexer 756.Thus, when a second path through the PN randomizer/de-randomizer 262B′,the differential encoder/decoder 264C′ and QPSK constellation mapper752A is selected, radio super frames 380 are conditioned fortransmission and reception according to QPSK format.

A second QPSK constellation mapper 752B is coupled to the differentialencoder/decoder 264A′ and to a PN randomizer/de-randomizer 262C′. TheQPSK constellation mapper 752B maps portions of the radio frame 350 toQPSK symbols according to quadrature phase-shift keying techniques(QPSK) identically to the QPSK constellation mapper 752A. Super frames380 are communicated between the QPSK constellation mapper 752B and themulti-plexer 756. Thus, when a third path through the differentialencoder/decoder 264A′, QPSK constellation mapper 752B and PNrandomizer/de-randomizer 262C′, is selected, radio super frames 380 areconditioned for transmission and reception according to QPSK format withspectrum spreading. Upon reception, super frames 380 routed through thisthird path are appropriately de-spreaded and decoded for communicationwith the framing block 260′.

So that the radio super frames 380 are properly received by a receivingterminal (e.g. the terminal 100 illustrated in FIG. 1), it is importantthe appropriate path is selected through the adaptive countermeasuresblock 616 for each radio super frame 380. This can be accomplished bythe transmitting terminal 100 notifying the receiving terminal 100′ ofthe manner and rate at which the transmitting terminal 100 istransmitting radio super frames 380.

FIG. 19 illustrates a chart of received signal level vs. time as aresult of rain fade. Refer to FIGS. 1 and 20 and assume that theterminal 100 is receiving data from the terminal 100′ via the wirelesslink 102. When rain occurs between the terminals 100 and 100′, the levelof the microwave carrier signal received by the terminal 100, thereceived signal level (RSL) falls over time as the rain increases overtime. Thus, depending upon the weather conditions, the RSL caneventually fall from a normal level to below threshold levels set atL1–L8. When the RSL is above the threshold level L1, this represents aninsubstantial level of rain fade. However, when the RSL is below thethreshold level L8, this represents a extreme level of rain fade. Thethreshold levels L2–L7 represent progressively increasing levels of rainfade between the extremes represented by L1 and L8. The rate at whichthe RSL falls (the measured slope) can also vary depending upon theweather conditions. Similarly, as the weather conditions improve, theRSL can return the normal level. In response to rain fade, the bit errorrate (BER) tends to rise. Thus, the adaptive countermeasures implementedby the present invention can detect the presence of rain fade bymeasuring the RSL or the BER.

In addition, the BER tends to rise in response to interference betweennearby wireless links. A significant difference between rain fade andinterference, however, is that in the event of interference, the RSL canremain at a normal level while the BER rises. Accordingly, the adaptivecountermeasures implemented by the present invention can detect theeffects of interference by measuring the BER.

Accordingly, in the preferred embodiment, the present invention respondsto both the measured RSL and the measured BER. To simplify the followingdiscussion, an example involves a response to rain fade detected bymeasuring the RSL. It will be apparent, however, that an identicalresponse can be made by measuring the BER. Thus, in the followingdiscussion, the BER, rather than the RSL, is compared to the variousthresholds disclosed (in addition, the operators >and <are exchangedwith each other). In addition, it will be apparent that a response canbe made simultaneously to both the RSL and to the BER with appropriatemodifications.

FIG. 20 illustrates a flow diagram for implementing counter-measuresaccording to the present invention in response to measured RSL. In thepreferred embodiment, the microprocessor 230 (FIG. 3) is appropriatelyprogrammed to implement the flow diagram illustrated in FIG. 20. In afirst state 800, the terminal 100 is configured for communicating dataat 16 QAM. Then, program flow moves from the state 800 to a state 802.In the state 802 a determination is made whether the RSL has fallenbelow the threshold level L1. If the RSL has not fallen below thethreshold level L1, then program flow returns to the state 800.

If, however, the RSL has fallen below the threshold level L2, thenprogram flow moves to a state 804. In the state 804, a determination ismade whether the rate at which the RSL is changing exceeds a firstpredefined slope Z1. If the rate does not exceed the predefined slopeZ1, then program flow moves from the state 804 to a state 806. In thestate 806, a determination is made whether the RSL has fallen below thethreshold L4. If the RSL has not fallen below the threshold L4, thenprogram flow returns to the state 800.

If, however, the RSL has fallen below the threshold L4, then programflow moves from the state 806 to a state 808. If the determination madein the state 804 resulted in a determination that the rate did exceedthe predefined slope Z1, then the program flow moves from the state 804to a state 808. In the state 808, the terminal is configured to transmitdata according to QPSK (without spectrum spreading). Then program flowmoves from the state 808 to a state 810.

In the state 810, a determination is made as to whether the RSL is abovethe threshold L5. If the RSL is above the level L5, then program flowmoves from the state 810 to a state 812. In the state 812, adetermination is made as to whether the rate at which the RSL ischanging exceeds a predefined slope Z2. If the rate exceeds the slopeZ2, then program flow returns to the state 800. If the rate does notexceed the slope Z2, then program flow moves from the state 812 to astate 814.

In the state 814, a determination is made whether the RSL is above thethreshold level L1. If not, then program flow returns to the state 808.If in the state 814, the RSL is above the threshold L1, then programflow returns to the state 800.

If, in the state 810, the RSL is not above the threshold L5, thenprogram flow moves to a state 816. In the state 816, a determination ismade whether the RSL is below the threshold L6. If the RSL is not belowthe threshold L6, program flow returns to the state 808. If, in thestate 816, the RSL is below the threshold 816, then program flow movesfrom the state 816 to a state 818. In the state 816, a determination ismade if the rate of change in the RSL exceeds a predefined slope Z3. Ifthe slope Z3 is not exceeded program flow moves from the state 818 to astate 820.

In the state 820, a determination is made whether the RSL is below thethreshold L8. If not, then program flow returns to the state 808. If inthe state 820 the RSL is not below the threshold L8, the program flowmoves to a state 822. In addition, if, in the state 818, the slope Z3 isexceeded, program flow moves to the state 822. In the state 822 theterminal 100 is configured for communicating data according to QPSK withspectrum spreading.

From the state 822, program flow moves to a state 824. In the state 824,a determination is made whether the RSL is below the threshold L7. Ifthe RSL is not below the level L7, then program flow returns to thestate 822. If, in the state 824, the RSL is above the threshold L7, thenprogram flow moves from the state 824 to a state 826. In the state 826,a determination is made whether the rate of change in the RSL exceeds apredefined slope Z4. If so, program flow returns to the state 808. If,in the state 826, the slope Z4 is not exceeded, then program flow movesto a state 828.

In the state 828, a determination is made whether the RSL is above thethreshold 828. If so, program flow returns to the state 808. If, in thestate 828, the RSL is not above the threshold 828, then program flowreturns to the state 822.

An important aspect of the present invention is that hysteresis isintroduced in the flow diagram for changing the manner of datacommunication in the states 800, 808 and 822, based upon the RSL. Thus,for example, to change from 16 QAM to QPSK, the RSL must fall below L2.However, to change from QPSK to 16 QAM, the RSL must rise above L1 whereL1 is higher than L2. This hysteresis reduces the frequency at which themanner of communicating data is changed and prevents oscillations fromoccurring between any two of the states 800, 808 and 822.

In a point-to-multipoint MAN, a single network node communicates radiosuper frames 380 with a plurality of other nodes. FIG. 21 illustrates apoint-to-multipoint metropolitan area network divided into sectorshaving inner and outer radii according to the present invention.

A single node at a hub 900 communicates with a plurality of subscribernodes, designated “r” located as various radial distances from the hub900 and in different directions (sectors). An important advantage of thepresent invention that changes in manner in which data is communicatedover a wireless link can be utilized to reduce interference betweennodes in a same sector, but at a different radial distances from the hub900.

As an example, assume a first subscriber node 902 is located in a sector904 at a radial distance from the hub 900 that is less than 2 Km. Assumethat a second subscriber node 906 is also located in the in the sector904 but at a radial distance from the hub 900 that is more than 2 Km andless than 4 Km. If both subscriber nodes 902, 906 communicate with thehub 900 in the same manner, there is a probability that communicationsintended for the node 902 will interfere with communications intendedfor the node 906. In the preferred embodiment of the present invention,however, the adaptive countermeasures block 616 (FIGS. 14 and 16) of thefirst subscriber node 902 is conditioned to communicate data in a firstmanner (e.g. according to 16 QAM), whereas, the adaptive countermeasuresblock 616 of the second subscriber node 906 is conditioned tocommunicate data in a second manner (e.g. according to QPSK). Theadaptive countermeasures block 616 of hub 900 is conditioned forcommunication with either of the nodes 902, 906, by changing back andforth between the first and second manner of communicating. This isaccomplished by appropriately conditioning the rate control signalapplied to the multiplexers 750, 756 (FIG. 18) of the hub 900 dependingupon which node 902, 906 the hub is currently communicating with.

In the preferred embodiment of the present invention, a securityauthentication protocol is implemented for data security purposesagainst eavesdroppers. FIG. 22 illustrates a wireless link 102 betweentwo terminals 100 and 100′ wherein an unauthorized terminal 950 isattempting to eavesdrop on communication between the two terminals 100,100′. Each terminal 100, 100′ and 950 is preconditioned to periodicallyauthenticate the other terminal opposite the communication link. Forthis purpose, each terminal is assigned a unique password.

Link authentication is accomplished in the following manner: Oncecommunication between the terminals 100 and 100′ is established, theterminals 100, 100′ exchange their passwords. Then, at periodicintervals, the terminal 100 sends a challenge message to the terminal100′. The challenge message includes an identification number and arandom number. The terminal 100′ receives the random number andcalculates a response based upon a mathematical combination of therandom number and its unique password. Then the terminal 100′ then sendsthe calculated response to the terminal 100 along with the sameidentification number it received.

The terminal 100 then matches the identification number it receives fromthe terminal 100′ to the challenge message it previously sent and thencompares the response it received to an expected response. The terminal100′ determines the expected response based upon its knowledge of theunique password associated with the terminal 100′ and upon its knowledgeof the random number included in the challenge. If the received responsematches the expected response, the terminal 100′ sends a success messageto the terminal 100′. Data communication then resumes. Each terminal100, 100′ periodically authenticates the other in a symmetrical manner.

If, however, the received response does not match the expected response,an alarm is set in the terminal 100. In response to the alarm, theterminal 100 maintains the wireless communication link 102 by sendingand receiving radio frames 350 (FIG. 6) with the terminal 100, however,the radio frames 350 sent by the terminal 100 no longer carry 100BASE-TEthernet data. Instead, the inter-packet gap code is sent. In addition,the terminal 100 is configured to no longer detect and separate100BASE-T Ethernet packets from received radio frames. Thus, the100BASE-T traffic in both directions is disabled. The terminals continueattempting to re-authenticate the link, and if successful, communicationof 100BASE-T packets resumes.

It is important to note that each terminal 100, 100′, 950, is configuredto successfully receive radio frames at all times, but us configured tosuccessfully receive 100BASE-T packet data only if it receives aresponse to a challenge message which matches an expected response. Thedetermination of whether a response to a challenge message isappropriate depends upon knowledge of the random number included in thechallenge message.

Assume that once the link 102 is established, the terminal 950 attemptsto eavesdrop. This is an unauthorized intruder who is attempting toreceive data from the link. It is expected in such a situation, that theterminal 950 will have its transmitter muted in an attempt to escapedetection. Because the transmitter of the terminal 950 is muted, itcannot authenticate with either terminal 100, 100′. Thus, although theterminal can receive responses to challenge messages sent by theterminals 100, 100′, it cannot match such a response to an expectedresponse because the terminal 950 will not have knowledge of the randomnumber sent with the response. Thus, an alarm will be set in theterminal 950. Once this occurs, the terminal 950 can no longer receive100BASE-T packet data. Accordingly, the attempted eavesdropping isprevented and data security maintained.

FIG. 23 illustrates an embodiment according to the present inventionhaving multiple digital processing MACs 222A″, 222B″ multiplexed to asingle radio framer 228″. The MACs 222A″, 222B″ can each be identical tothe MAC 222′ illustrated in FIG. 16 while the radio framer 228″ can beidentical to the radio framer 228′ illustrated in FIG. 16. Thisembodiment enables multiple 100BASE-T Ethernet packets to be receivedsimultaneously, one for each MAC 222A″, 222B″. The Ethernet packets aretemporarily stored in each MAC 222A″, 222″ and then provided to theradio framer 228″ via a multiplexer 980 according to time divisionmultiplexing. The time division multiplexed data is then communicatedover the wireless link 102. According to this embodiment, the wirelesslink 102 is configured to communicate data at 200 Mbps. It will beapparent that a number, n, of MACs can be coupled to the multiplexer 980thereby achieving a n×100 Mbps data rate for the wireless link 102. Suchan arrangement is limited by the maximum bandwidth capacity for thewireless link 102.

The present invention has been described in terms of specificembodiments incorporating details to facilitate the understanding of theprinciples of construction and operation of the invention. Suchreference herein to specific embodiments and details thereof is notintended to limit the scope of the claims appended hereto. It will beapparent to those skilled in the art that modifications may be made inthe embodiment chosen for illustration without departing from the spiritand scope of the invention. Specifically, it will be apparent to one ofordinary skill in the art that the device of the present invention couldbe implemented in several different ways and the apparatus disclosedabove is only illustrative of the preferred embodiment of the inventionand is in no way a limitation.

1. A method of synchronizing Fast Ethernet data packets to radio frames,the method comprising steps of: a. receiving Fast Ethernet data packets;b. storing packet data from the Fast Ethernet data packets in a packetbuffer wherein the step of storing is performed according to a firstclock signal wherein the first clock signal is derived from the FastEthernet data packets; c. retrieving the packet data from the packetbuffer thereby forming retrieved packet data wherein the step ofretrieving is performed according to a second clock signal wherein thesecond clock signal is asynchronous with the first clock signal; and d.formatting the retrieved packet data according to radio frames; whereinthe method does not include a step of converting the packet data into atelephony communication protocol or into an asynchronous transfer mode(ATM) protocol prior to communication of the radio frames over thewireless link.
 2. The method according to claim 1 wherein the step offormatting is performed according to the second clock signal.
 3. Themethod according to claim 2 wherein the second clock signal is higherthan the first clock signal.
 4. The method according to claim 2 whereinthe step of formatting includes a step of removing a data valid bit fromeach four-bit portion of retrieved packet data.
 5. The method accordingto claim 2 wherein the step of storing includes a step of removing apreamble from each Fast Ethernet data packet.
 6. The method according toclaim 5 wherein the step of storing further includes steps of: a.determining a length of the packet data for each Fast Ethernet datapacket; and b. storing the length of the packet data in a length buffer.7. The method according to claim 6 wherein the step of formattingfurther includes a step of inserting the length of the packet into theradio frame.
 8. The method according to claim 7 wherein the step offormatting further includes a step of inserting a check sum for thelength into the radio frame.
 9. The method according to claim 8 whereinthe check sum is a Golay check sum.
 10. The method according to claim 2wherein the step of formatting includes steps of: a. performing forwarderror correction on the retrieved packet data thereby forming errorcorrected packet data; and b. inserting the error corrected packet datainto a data field of a radio frame.
 11. The method according to claim 10wherein the step of formatting further includes a step of randomizingthe data field of the radio frame.
 12. The method according to claim 10wherein the radio frames each have a same length and wherein the step offormatting the retrieved packet data is performed such that boundariesfor the data packets are not necessarily aligned with boundaries for theradio frames.
 13. The method according to claim 10 wherein the step offormatting further includes a step of time-division multiplexing thedata packets into the radio frames.
 14. An apparatus for synchronizingFast Ethernet data packets to radio frames, the apparatus comprising: a.a packet transceiver for detecting Fast Ethernet data packets; b. apacket buffer coupled to the packet transceiver for temporarily storingpacket data from the data packets according to a first clock signalderived from the data packets; c. a packet retriever coupled to thepacket buffer for retrieving the packet data from the packet bufferthereby forming retrieved packet data wherein the packet retrieverretrieves the packet data according to a second clock signal and whereinthe second clock signal is asynchronous with the first clock signal; andd. a radio framer coupled to the packet retriever for formatting theretrieved packet data into radio frames; wherein the Packet data is notconverted into a telephony communication protocol or into anasynchronous transfer mode (ATM) protocol prior to communication of theradio frames over the wireless link.
 15. The apparatus according toclaim 14 wherein the radio framer formats the retrieved packet data inradio frames according to the second clock signal.
 16. The apparatusaccording to claim 15 wherein the second clock signal is higher than thefirst clock signal.
 17. The apparatus according to claim 15 wherein theradio framer removes a data valid bit from each four-bit portion of theretrieved packet data.
 18. The apparatus according to claim 15 apreamble is removed from each Fast Ethernet data packet prior to storageof the packet data in the packet buffer.
 19. The apparatus according toclaim 18 further comprising a length buffer coupled to the radio framerfor storing a length of packet data for each Fast Ethernet data packet.20. The apparatus according to claim 19 wherein the radio framer insertsthe length of packet data for each Fast Ethernet data packet from thelength buffer into the radio frames.
 21. The apparatus according toclaim 20 wherein the radio framer inserts into the radio frames a checksum for the length of packet data for each Fast Ethernet data packet.22. The apparatus according to claim 21 wherein the check sum is a Golaycheck sum.
 23. The apparatus according to claim 15 wherein the radioframer comprises: a. a forward error corrector for correcting errors inthe retrieved packet data thereby forming error corrected data; and b. aframing apparatus coupled to the forward error corrector for insertingthe error corrected data into a data field of a radio frame.
 24. Theapparatus according to claim 23 wherein the radio framer furthercomprises a randomizer coupled to the framing apparatus for randomizingthe data field of the radio frame.
 25. The apparatus according to claim23 wherein the radio frames each have a same length and wherein theframing apparatus inserts the error corrected data into the data fieldsuch that boundaries for the data packets are not necessarily alignedwith boundaries for the radio frames.
 26. The apparatus according toclaim 23 wherein the framing apparatus time-division multiplexes theerror corrected data into the radio frames.
 27. The apparatus accordingto claim 14 further comprising a packet counter coupled to the packetbuffer for maintaining a count of Fast Ethernet data packets stored inthe buffer.
 28. The apparatus according to claim 27 further comprisingarbitration logic means coupled to the packet buffer and to the packetcounter for determining when packet data corresponding to a completeFast Ethernet packet has been stored in the packet buffer and fordetermining when the packet data corresponding to a complete FastEthernet packet has been retrieved from the packet buffer.
 29. Theapparatus according to claim 28 further comprising a threshold comparemeans coupled to the packet counter for determining when the count isequal to or greater than a predetermined threshold number.
 30. Theapparatus according to claim 29 further comprising a packet readingmeans coupled to the threshold compare means for providing an initiationsignal when the count exceeds the predetermined threshold.
 31. Theapparatus according to claim 30 wherein the predetermined threshold isone.
 32. The apparatus according to claim 30 wherein the radio framerforms a frame enable signal when the radio framer is ready to receivepacket data and wherein the apparatus further comprises a logic gatecoupled to receive the initiation signal and the frame enable signal,the logic gate for initiating of retrieval of packet data from thepacket buffer.
 33. An apparatus for synchronizing radio frames to FastEthernet data packets, the apparatus comprising: a. asynchronizer/de-synchronizer for recovering packet data for FastEthernet data packets from radio frames received from a wireless link;b. a packet buffer coupled to the synchronizer/desynchronizer fortemporarily storing packet data from the radio frames according to afirst clock signal synchronous with the radio frames; c. a packetretriever coupled to the packet buffer for retrieving the packet datafrom the packet buffer thereby forming retrieved packet data wherein thepacket retriever retrieves the packet data according to a second clocksignal and wherein a frequency of the second clock signal is lower thana frequency of the first clock signal; and d. an Ethernet transceivercoupled to the packet retriever for forwarding the Ethernet data packetsreconstructed from the radio frames; wherein the method does not includea means for converting the packet data into a telephony communicationprotocol or into an asynchronous transfer mode (ATM) protocol prior tocommunication of the radio frames over the wireless link.
 34. Theapparatus according to claim 33 wherein the packet retriever adjusts afrequency of the second clock signal according to an amount of spaceavailable in the packet buffer.
 35. The apparatus according to claim 33wherein the packet retriever adjusts an inter-packet gap for the FastEthernet data packets according to an amount of space available in thepacket buffer.
 36. The apparatus according to claim 33 wherein alayer-two switch at an opposite end of the wireless link is selectivelypaused according to an amount of space available in the packet buffer.37. An apparatus for synchronizing radio frames to Fast Ethernet datapackets, the apparatus comprising: a. a synchronizer/de-synchronizer forrecovering packet data for Fast Ethernet data packets from radio framesreceived from a wireless link; b. a packet buffer coupled to thesynchronizer/desynchronizer for temporarily storing packet data from theradio frames according to a first clock signal synchronous with theradio frames; c. a packet retriever coupled to the packet buffer forretrieving the packet data from the packet buffer thereby formingretrieved packet data wherein the packet retriever retrieves the packetdata according to a second clock signal and wherein at least sufficientpacket data for a complete one of the Ethernet data packet is stored inthe packet buffer prior to the packet retriever retrieving the packetdata; and d. an Ethernet transceiver coupled to the packet retriever forforwarding the Fast Ethernet data packets reconstructed from the radioframes; wherein the method does not include a means for converting thepacket data into a telephony communication protocol or into anasynchronous transfer mode (ATM) protocol prior to communication of theradio frames over the wireless link.
 38. The apparatus according toclaim 37 wherein the packet retriever adjusts a frequency of the secondclock signal according to an amount of space available in the packetbuffer.
 39. The apparatus according to claim 37 wherein the packetretriever adjusts an inter-packet gap for the Fast Ethernet data packetsaccording to an amount of space available in the packet buffer.
 40. Theapparatus according to claim 37 wherein the a layer-two switch at anopposite end of the wireless link is selectively paused according to anamount of space available in the packet buffer.
 41. A method ofsynchronizing radio frames to Fast Ethernet data packets, the methodcomprising steps of: a. recovering packet data for Fast Ethernet datapackets from radio frames received from a wireless link; b. storingpacket data from the radio frames in a packet buffer according to afirst clock signal synchronous with the radio frames; c. retrieving thepacket data from the packet buffer thereby forming retrieved packet datawherein the step of retrieving is performed according to a second clocksignal and wherein a frequency of the second clock signal is lower thana frequency of the first clock signal; and d. forwarding the FastEthernet data packets reconstructed from the radio frames; wherein themethod does not include a step of converting the packet data into atelephony communication protocol or into an asynchronous transfer mode(ATM) protocol prior to communication of the radio frames over thewireless link.
 42. The method according to claim 41 further comprising astep of adjusting a frequency of the second clock signal according to anamount of space available in the packet buffer.
 43. The method accordingto claim 41 further comprising a step of adjusting an inter-packet gapfor the Fast Ethernet data packets according to an amount of spaceavailable in the packet buffer.
 44. The method according to claim 41further comprising a step of initiating a pause to a layer-two switch atan opposite end of the wireless link according to an amount of spaceavailable in the packet buffer.
 45. A method of synchronizing radioframes to Fast Ethernet data packets, the method comprising steps of: a.recovering packet data for Fast Ethernet data packets from radio framesreceived from a wireless link; b. storing packet data from the radioframes in a packet buffer according to a first clock signal synchronouswith the radio frames; c. retrieving the packet data from the packetbuffer thereby forming retrieved packet data wherein the step ofretrieving is performed according to a second clock signal and whereinat least sufficient packet data for a complete one of the Fast Ethernetdata packet is stored in the packet buffer prior to retrieving thepacket data; and d. forwarding the Fast Ethernet data packetsreconstructed from the radio frames; wherein the method does not includea step of converting the packet data into a telephony communicationprotocol or into an asynchronous transfer mode (ATM) protocol prior tocommunication of the radio frames over the wireless link.
 46. The methodaccording to claim 45 further comprising a step of adjusting a frequencyof the second clock signal according to an amount of space available inthe packet buffer.
 47. The method according to claim 45 furthercomprising a step of adjusting an inter-packet gap for the Fast Ethernetdata packets according to an amount of space available in the packetbuffer.
 48. The method according to claim 45 further comprising a stepof initiating a pause to a layer-two switch at an opposite end of thewireless link according to an amount of space available in the packetbuffer.